Ducting is commonly used in large buildings such as factories, office blocks and apartment blocks for the transmission of air, which may be for the purposes of heating or cooling an environment in a building, or ventilating a building. Typically, such ducts are used to transport heated or cooled air. Where climatic conditions are such that the difference between the temperature of the ambient temperature of the atmosphere to be heated or cooled is relatively dose to the temperature of the heated or cooled, for example 3 or 4 degrees C., ducts have historically been formed from sheet steel, and have been un-insulated.
In locations where climatic conditions are more extreme, heat loss or gain by the heating/cooling air in the duct can pose a significant problem, which has resulted in ducts being insulated in those environments to maintain the desired temperature of the conveyed air and to conserve energy. First attempts at insulating ducts consisted of lagging ducts with a material having insulating properties. However, such work is labour intensive and time consuming. Furthermore, lagging ducts with traditional insulating materials detracts from the sectional nature of duct work, i.e. being sectional in nature duct work is relatively simple to assemble and disassemble. Lagging in insulating material makes disassembly more difficult.
One solution proposed involves making ducts from insulating boards. Ducts made from such insulating boards are used widely in countries having extreme climates, both hot and cold. Even in more temperate climates the desire to increase the efficiency of heating and air conditioning systems is leading to insulated ducting being specified more frequently by architects and civil engineers.
One problem associated with ducts made from insulated boards is that the method of connecting one section of duct to another is time consuming due to the parts being relatively complex, and fitters not using the connecting method regularly. This results in insulated ducts being more expensive to install.
In the known method of connecting ducts made from insulated boards the end of a duct section is provided with a bracket, a part of which extends beyond the outer edge of the duct section. When the ends of two duct sections are aligned a cleat is forced over two abutting brackets. If there is any misalignment between the duct sections, forcing the cleat onto the brackets can be extremely difficult.
The known method of connecting ducts made from insulated boards is very different from methods used to connect un-insulated ducts. There are circumstances involving a requirement to connect an un-insulated duct to an insulated duct, for example where cool air is being conveyed and the duct passes through an environment having an elevated temperature. Connecting insulated and uninsulated ducts together posses significant problems to the installer.
It would therefore be desirable to improve the connection of one section of duct to another.